Earth moving equipment, such as a motor grader for example, often must operate in environments with poor footing conditions. Some earth moving machines are equipped with an all wheel drive system so that the front wheels of the machine, normally used for steering, are driven to help propel the machine in these poor footing conditions. Normally, only the rear wheels are driven, but when poor footing conditions are encountered causing excessive wheel slip, the front wheels of an all wheel drive machine can be driven to increase traction of the machine thereby reducing slip and maintaining directional control. When all wheels are in poor footing conditions, such as when working on side slopes, or maximum traction is desired, the machine can be operated in an all wheel drive mode. Operating a motor grader in an all wheel drive mode for maximum traction may be desirable when the motor grader is performing a cutting operation, such as cutting a new road or grading a severe side slope. The all wheel drive mode is also useful when a motor grader is used for removing snow from a roadway.
In a motor grader, depressing a brake pedal normally applies brake pressure to the rear wheels, which are the driven wheels, to stop the machine. The same is true for an all wheel drive machine. It can be appreciated that it would be highly desirable to also brake the front wheels when operating in an all wheel drive mode. Braking the front wheels could improve braking response and increase the life of the rear wheel braking system because the front wheels would assume part of the braking load.